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Wednesday, March 18, 2015

Access to Quality Transit credit?Prove it!

The intent
behind USGBC’s Access to Quality Transit is to encourage development in areas
that are connected by public transportation systems to reduce car usage…but do
people want to live in areas that are highly connected to public
transportation?In other words, could
the effect that multiple modes of transportation have on where people live be
displayed?Using a geographic
information system and publicly available data, this article explores these questions
and gets to, “Yes”.

The public
transportation network in Boston is expansive and goes far beyond the city
limits.The system is comprised of four
modes of transportation; subways, commuter rails, buses, and ferries, each with
entry points consisting of stations, stops, or docks.The systems operate independently from one
another, but are complementary in that together they provide greater access to
larger areas of the City.

The area around
the entry points needs to be determined in order to develop answers to the
posed questions.Working with each
system separately, a 1-mile buffer zone was created and merged together around
each of the entry points for each respective system creating images as
displayed in Figure 1 below.

Figure
1

SubwayCommuter Rail

Bus Ferry

Overlaying these buffers with the Year 2000 U.S. Census Data provides an
understanding of each system’s influence on attracting people.Using the buffers’ areas and the population
captured by them enabled calculation of the population density around the entry
points.These results can be seen in
Table 1 below which is ranked from greatest population density to least.

Table 1

Mode

Sq. Miles

Population

Pop / mi2

Subway

95

995,552

10,479

Commuter
Rail

353

1,742,280

4,936

Bus

488

2,228,490

4,567

Ferry

75

261,307

3,484

However,
what about the effects of multiple modes of transportation?Overlaying the individual mode-buffers
described above creates areas where there are 1-, 2-, 3-, and 4-modes of
transportation available.For instance,
areas where there is only a subway or commuter rail station, a bus stop, or a
ferry dock is ranked as 1-mode, not distinguishing between the mode types.Areas where all four mode buffers overlapped
are ranked as 4-mode, and any combination of 2 and 3 different mode types are
ranked as 2- and 3-mode areas.A graphic
displaying the results of these combinations can be seen if Figure 2 below.

Figure 2

Overlaying
these new buffers with the census data shows the impact that multiple modes of
transportation have on where people want to live.These outputs can be seen in Table 2 below
where the influence can be clearly seen.; as the number of available modes
increase, so does the number of people living in those areas.

Table 2

Area

Sq. Miles

Population

Pop / mi2

1 Mode

507

1,493,635

2,946

2 Mode

175

1,172,938

6,703

3 Mode

45

572,605

12,725

4 Mode

5

64,969

12,994

So what does
this all mean?That the Access to
Quality Transit credit is in the right direction, people want to live in areas
that are highly connected to public transportation systems.